Air intake and exhaust silencer for internal-combustion engines



June 1950 A. BLUNDELL 2,512,823

AIR INTAKE AND EXHAUST SILENCER FOR INTERNAL-COMBUSTION ENGINES FiledApril 22, 1946 2 Sheets-Sheet l pnweml'w Wual [Ml/71M June 27, 1950BLUNDELL 2,512,823

AIR INTAKE AND EXHAUST SILENCER FOR INTERNAL-COMBUSTION ENGINES FiledApril 22, 1946 2 Sheets-Sheet 2 6 FIQ.3. F-IQ.4.

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Patented June 27, 1950 AIRINTAKE ANDEXHAUST SILENCER FORINTERNAL-COMBUSTION ENGINES Alfred Blundell, Coleshill, EnglandApplication April 22, 1946, Serial .No. 663,893 In Great Britain May 2,1945 .2 Claims- (Cl. 181-47) This invention relates to the attenuationof sound waves and more particularly to the reduction or elimination ofthe noises occurring in the induction and also the exhaust systems ofinternal combustion engines.

The sound waves producing these noises are of 'ahighly complex order andinclude .both high and low frequency bands the amplitude and ratio ofwhich vary with diflerent engines and different designs of induction orexhaust systems for the same engine.

For this season it has previously been considered necessary to dealseparately with the high and the low frequencies and to provideapparatus for this purpose involving an elaborate system of cylindricalchambers traversed by an open-ended tube in acoustic connectiontherewith and adapted for connection with, or formed as part of theinduction pipe. The process of acoustical impedance being the combinefunction of a sound wave passage and a capacity chamber, the combinationbeing acoustically adapted to suit individual frequency bands the soundwave passage being the inertance component and the chamber being thecapacitance component, the combine function in series performing thefunction of acoustic impedance.

The object of the invention .is to provide a silencer which, although ofextremely simple construction and whose linear dimensions are small ascompared with the major wavelengths of the noise frequencies dealt with,will efiectually attenuate sound waves of both high and low frequencies,by the process of acoustical impedance and sound wave reflection, theentire function occurring within the same chamber and same fluid mass.Therefore the function of the components of inertance and capacitance inseries occurring within the same fluid medium or media.

The communication to the chamber of the silencer from the engine airintake or exhaust system may be at any angle to the axis of the chamberi. e. at right angles, parallel or co-axial therewith.

Furthermore the communication to the aforesaid chamber may be via acylindrical or spherical chamber formed at the apex of the firstmentioned conical chamber and in direct communication therewith.

Particularly in the case of exhaust silencers the central conduit may beextended into the apex of said conical chamber, said conduit beingperforated at that end.

Referring to the drawings,

Figures 1 and 2 are perspective, and longitudinal cross sectional viewsof a preferred embodiment of the present invention.

Figures 3 and 4 are sectional views of simplified versions of thepresent invention.

Figure 5 is a development in longitudinal section of the silencer shownin Figure 3 and,

Figure 6 is an example of the present invention applied to the exhaustsystem of an internal combustion engine.

Refer-ring toFigures 1 and 2, the conical-chamber I i closed at itslarger end 2 in interiorly concave fashion, said end 2 carrying aconduit 3 open at both ends and co-axial with the axis of the conicalchamber I.

At the apex 4 of the conical chamber l is formed a spherical chamber 5indirect communication with the conical chamber l and also adapted tocommunicate with the engine induction system via the opening 6.

In Figure 3 the opening 5 to the induction system is-co-axial with theaxis of the conical chamher I and conduit 3.

In Figure 4 a cylindrical connecting chamber 1 is shown between theinduction connection 6 and the conical chamber I.

Figure 5 shows a development of Figure 3 in which a second conicalchamber 8 is arranged coaxial with the first conical chamber l in suchamanner that the larger end of the first conical chamber 1 communicatesvia ports 9 with the apex end of the second conical chamber 8.

With reference to Figure 7, the invention is shown applied to theexhaust system of an engine wherein the conical chamber I is connectedto the rear end of an orthodox silencer. However, the central conduit 3in this case is preferably provided with perforations ID at the innerend. Alternatively the silencer may be incorporated within thecylindrical casing of an orthodox silencer in either case the exhaustpipe I I is a continuance of the central conduit 3. If desired thesilencer for the exhaust system can be of the type shown in Figure 5.

For increased silencing efiiciency any of the above referred tosilencers may be coupled in series in any suitable Way.

With reference to the drawings generally the operation of the silenceraccording to the present invention is as follows:

Due to the stream of air or gas or fluid mass generally from the centralconduit 3 to the engine via the opening 6 in the case of the inductionsystem and from the opening 6 to the conduit 3 in the case of theexhaust system due to inertia of the fluid stream, and in conjunctionwith the shape of the chamber, the fluid in the apex end of the chamberis in a turbulent and high state of motion, as compared with the fluidcondition in the wide end of the chamber, the pulsation and circulationmotion being relatively small. Thus Without any physical means ofseparation between the system and the chamber, there exists in theconical chamber l two fluid media or medium one in a high state ofturbulence and inertia and one in a quiescence state. The chambers shapeperformin the agent of conductivity, always being automatic, for anyposition selected by the central conduit, for any combination of themedia of response and attenuation.

The relative proportions of these two media can be varied quite readilyand to a considerable degree by adjusting the length of the centralconduit 3 within the chamber I and/or altering its diameter beforeresorting to alteration of the dimensions of the conical chamber.

In all cases sound waves of a highly complex order emanate from theengine via the opening 6 into the silencer.

The effect of the turbulent fluid mass is that of inertance and theeffect of the quiescence fluid mass that of capacitance, the resultgiving rise to acoustic impedance, in which the high and low frequenciesare attenuated, resulting in a mean frequency which is also attenuatedby interference due to reflection between the cone apex and sides andthe end plate diaphragm 2.

The apex volume of the chamber as well as performing the function ofinertance also acts as a mean response for the combine noise frequenciesand therefore the adjustment of the central conduits internal and withinthe chamber selects the most suitable response characteristic mostadaptable for the attenuating characteristics of the apparatus.

The conical sides of the chamber are instrumental in the conductivity ofthe sound waves for the process of attenuation and act as conductors inseries for any combination of the two media, thus eliminating anyphysical agent of conductivity from the source of sound other than thatof the chamber sides.

By the provision of a spherical chamber 5 Figures 1 and 2 or acylindrical chamber 1, Figure 4 the function of a resonator is providedto assist in the attenuation of the sound waves and, moreover, therequired length of the conical chamber l is reduced.

If the length of the silencer requires a further reduction in length toadapt it for working conditions the construction may be that shown inFigure 5 where the effect is that of two conical chambers l and 8 inseries in direct communication with one another via the ports 9.

With reference to Figure 3, A, B and C represent the positions of theend of the central conduit 3 for high medium and low frequenciesrespectively, either position being obtained by axial adjustment of theconduit.

I claim:

1. A silencer for the induction or exhaust systems of internalcombustion engines comprising in combination a truncated conicalchamber; an outwardly convex end wall to the larger end of said chamber;a single open ended conduit mounted in and passing through said end walland extending into and partially through said chamber, and a furtheraperture provided in said chamber adapted to be connected to the engine,all so arranged that a direct flow of gas is permitted between saidconduit and the said further aperture.

2. A silencer for the induction or exhaust systems of internalcombustion engines comprising in combination a truncated conicalchamber; a second truncated conical chamber surrounding said firstchamber the smaller end of said second chamber communicating with saidfirst chamber at the larger end thereof via ports at said larger end; anoutwardly convex end wall to the larger end of said first chamber; asingle open ended conduit mounted in and passing through said end walland extending partially through said flrst chamber, and a, furtheraperture provided in said first chamber adapted to be connected to theengine, all so arranged that a direct flow of gas is permitted betweensaid conduit and the said further aperture.

ALFRED BLUNDELL.

REFERENCES CETED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,489,422 Brabant Apr. 8, 19241,874,326 Mason Aug. 20, 1930 2,088,576 Compo Aug. 3, 1937 2,101,850Green Dec. 14, 1937 2,252,256 Harris Aug. 12, 1941 FOREIGN PATENTSNumber Country Date 382,418 Great Britain Oct. 27, 1932 817,517 FranceApr. 9, 1937 833,214 France July 18, 1938 363,199 Italy Sept. 21, 1938

